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WATCH: Emergency teams help the wounded shortly after the blast. Reuters video

An explosion at a cafe in Russia's North Caucasus has wounded at least 20 people in the latest incident of violent unrest in the region.

The explosion occurred outside a cafe in downtown Pyatigorsk. A spokesman for the Stavropol regional police, Stanislav Belyayev, said the wounded were cafe customers and people who were just passing by.

Belyayev said all the injured were taken to hospital and three were in serious condition. He said a powerful homemade explosive was planted in a Lada that was parked outside the cafe.

Russian President Dmitry Medvedev has ordered the Federal Security Service and Prosecutor-General's Office to identify and capture those responsible for the bombing. Investigators are treating the incident as a terrorist attack.

Just hours earlier, a suicide bomber blew himself up as he approached a checkpoint on a road near Vladikavkaz, the provincial capital of North Ossetia.

Regional police spokesman Aslan Dzgoyev said the bomber, who died in the explosion, was accompanied by two other men. One was captured after police shot and wounded him and the other escaped.

Both incidents are part of a deadly pattern of violence in the North Caucasus, where the Kremlin has been trying without success to quell an Islamist insurgency.

Violence has become commonplace in the region in the wake of two Chechen wars for independence in the mid-90s and from 1999 through 2009.

This past May, at least five people were killed and 20 injured when a bomb exploded outside a theater in Stavropol just before the start of a Chechen dance show. No one claimed responsibility.

The most notorious attack happened in 2004, when Islamist militants seized a school in the North Ossetia town of Beslan. Of the 330 people killed, more than half were children.

The site of the August 17 cafe bombing -- Pyatigorsk -- was chosen last year by the Kremlin to be the administrative centre of the new North Caucasus Federal District.

Moscow created the new district in an attempt to reorganize the region's provinces into groups of Muslim and Christian Orthodox communities, in a effort to prevent further violence.